Getting the value from python script into a powershell script

Question

I have python script which creates a ticket. I need to invoke the python script from within powershell script and get the ticketnumber(12 digit long).

Approach#1:

I tried to use the exit(ticket_number) to get this done.It worked well as long as the number is not very large.

Ex.

exit(12345) from python translates to $LASTEXITCODE=12345 #good
exit(123456789123) from python translates to $LASTEXITCODE=-1 #not sure what is going wrong here

    dummy.py
    --------
    print("hello")
    exit(123456789123)
       
    sample.ps1
    ----------
    python dummy.py
    Write-Host($LASTEXITCODE)

Approach#2:

Use of env variable

dummy.py
--------
import os
os.environ["TICKETNUMBER"] = "123456789123"
exit(0)

sample.ps1
----------
Get-ChildItem -Path Env:TEMP # good - able to get value
Get-ChildItem -Path Env:TICKETNUMBER # - error - ItemNotFoundException

So, I would like to know what is going wrong in each of the approaches. Are there any better approaches to get this done - Please suggest.

Jacob Colvin · Accepted Answer · 2020-07-17 06:18:49Z

You should not use exit codes to output a value, this simply isn't what they're meant to do. You can read more about exit codes here: https://shapeshed.com/unix-exit-codes/#what-is-an-exit-code-in-the-unix-or-linux-shell

Environment variables only work for passing around values when you're passing them to children. If you spawn a new process, said process will inherit the environment variables in scope of your current session. However, you can't change the environment variables of the parent (your session) from the child (the python runtime). Thus, in Powershell, your "TICKETNUMBER" environment variable is out of scope.

First of all let me say that there are many different ways to go about solving this. The solution that requires the least amount of work on your part would be to output to stdout, which allows you to output values for consumption by other processes. You can do this with print in python. You already did this but likely ran into issues due to your use of exit codes.

In Powershell, you can accept this input via the pipeline. There are a lot of ways to go about this, but in your example the $input variable will work.

dummy.py
--------
print("123123123")

sample.ps1
--------
Get-ChildItem -Path $input

You can then run py dummy.py | ./sample.ps1, which will return the directory listing of "./123123123".

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